1. Field of the Invention
This invention relates generally to methods of controlling pulsed lasers, and more particularly, to a method of cavity dumping lasers to generate high repetition rates with frequency modulation.
2. Description of the Prior Art
In applications of lasers to communication systems there exist a requirement that the lasers operate at a high frequency, generally, 100 to 1000 kilopulses per second (kpps). These pulses can be generated by cavity dumping the laser. In order to achieve bit error rates of 10.sup.-6 or lower, the energy per pulse must be stabilized. The percentage of pulses below a specific minimum energy level must be very small. While cavity dumping at a constant frequency may be stable, data encoding by pulse interval modulation, as well as various noise sources, introduce large variations in output pulse energy. A method of controlling the buildup of circulating power in the laser must be implemented, so that the amount of energy in the cavity at the time of cavity dumping is nearly constant. The method of control must be adaptable to work over the operating range of the laser. In two-way communication systems, the laser controls must not cause energy to leak out of the laser between pulses, since such energy increases the background noise for the receiving part of the communication system. It would be desirable if there was provided a laser and laser controller that regulated the circulating power buildup, thereby controlling the output pulse energy levels and providing a control loop which maintains a low level of circulating power in the laser cavity between pulses until a fixed time before the next output pulse would occur.